Current methods of trans pars plana vitrectomy utilize suction force to imbricate the vitreous to be cut into the port of the vitrectomy machine. The surgical assistant provides a suction by manipulating a five to fifty cc plastic syringe while observing the surgeon's operative field through a stereo observation tube on the operating microscope. Advantages of this method are its inherent simplicity and the possibility of rapid reversal of the suction to disengage tissue from the cutting opening.
The prior art syringes which have been utilized in this method must be held by the surgical assistant with both hands to control the amount of suction. Due to friction in the syringe and the fatiguing effect to the assistant's fingers, the feel of suction level is greatly impaired causing imprecise response in time and pressure. To overcome this lack of precision and this difficulty of operation, a device which can be operated more precisely and more easily and with only one hand is necessary.
U.S. Pat. No. 2,771,217, issued to Brown et al. shows a measuring and dispensing device which may be operated only by one hand. While this device frees one of the operator's hands, it does not provide the sensitivity necessary to determine the amount of suction or pressure that is necessary. This is due in part to the use of a bushing seal, a threaded bore and detents so as to obstruct the sense of feel of the operator. Additionally, Brown's device was never meant to operate as the conventional, disposable syringe since it has no means to hold such a syringe and therefore could not even be applied to the vitreous operation previously described.